The role of the orifice plate
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Release Time：2020-07-16
When the pressure difference between the front and back of the pipeline is large, the method of increasing the orifice plate is usually used. The principle is that when the fluid flows in the pipeline, due to the local resistance of the orifice plate, the pressure of the fluid decreases and the energy is lost. This phenomenon is thermodynamically called throttling. This method is simpler than using a regulating valve, but a suitable method must be selected, otherwise the liquid is prone to cavitation and affects the safe operation of the pipeline.
When the pressure difference between the front and back of the pipeline is large, it is usually increased.Throttle orifice plateThe method. The principle is that when the fluid flows in the pipeline, due to the local resistance of the orifice plate, the pressure of the fluid decreases and the energy is lost. This phenomenon is thermodynamically called throttling. This method is simpler than using a regulating valve, but a suitable method must be selected, otherwise the liquid is prone to cavitation and affects the safe operation of the pipeline.
Throttle orifice plateThe function is to reduce the hole diameter of the pipe in the appropriate position. When the liquid passes through the neck, the fluid will become thinner or shrink. The smallest cross section of the flow occurs downstream of the actual necking and is called the necking cross section. The flow rate is the largest in the contraction section, and the increase in flow rate is accompanied by a significant decrease in the pressure in the contraction section. As the airflow expands to a larger area, the velocity decreases and the pressure increases, but the downstream pressure does not fully recover to the upstream pressure due to greater internal turbulence and energy consumption. If the pressure pvc at the constricted section is lower than the saturated vapor pressure pv at the corresponding temperature of the liquid, the vapor and gas dissolved in the water will escape from the flow, forming small bubbles mixed with the vapor and gas. The lower the pressure, the more bubbles. IfThrottle orifice plateThe downstream pressure p2 is still below the saturated vapor pressure of the liquid, then bubbles will continue to be generated in the downstream pipe and a liquid-vapor two-phase mixture will be present, which is called flash evaporation. If the downstream pressure is restored to be higher than the saturated vapor pressure of the liquid, the bubbles will condense and burst quickly under the action of high pressure. At the moment of bubble collapse, a local cavity will be generated, and high-pressure water will flow to these original bubbles at a very high speed. The occupied space forms an impact force. Because the gas and steam in the bubbles cannot be dissolved and condensed in an instant, they are divided into small bubbles under the impact force, and then compressed and condensed by high-pressure water, forming multiple repetitions, and producing similar to what we can imagine flowing through the pipe The noise of sand and gravel. This phenomenon is called cavitation. Under the action of water hammer pressure, the surface of the runner material appears fatigue and serious damage.Throttle orifice plateThe whole process of development and rupture so that the material is destroyed is called cavitation.
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